The invention is in the field of photo flash lamp arrays, such as the Flip Flash type of array.
U.S. Pat. No. 4,133,023 to Hanson discloses a Flip Flash type of array having a plurality of high-voltage flash lamps and their reflectors positioned in front of a circuit board. The circuit board is shaped to provide connector tabs for connection to a camera socket. Each connector tab carries a plurality of connection terminals which include an electrical ground or "common" terminal. Circuits runs carried on the board connect the terminals to the lamps and to circuitry whereby a lamp is flashed each time a firing voltage pulse is applied to the terminals. "Common" circuit runs on the board connect a lead-in wire of each flash lamp to the common connection terminals. A metal foil shield is positioned behind and parallel to the circuit board and is electrically connected to the common circuit runs and terminals by suitable conductive means such as a wire staple through the center of the circuit board.
The circuit runs on Flip Flash circuit boards are formed with a conductive ink containing silver. Given the high cost of silver, multiplied by the tens of millions of Flip Flash arrays manufactured per year, the cost of the circuit run material is considerable and it would be desirable to reduce this cost.
The above-referenced patent application discloses a flash array having a circuit board on which the circuit runs are made from an inexpensive material comprising carbon particles applied to the board in a liquid binder which is then dried and evaporated. These circuit runs have a considerably higher resistance (generally 30 or 40 times, or more) than the previously employed silver-containing conductive ink. Flash arrays having the high-resistance circuit runs have an increased tendency for lamps to accidentally flash due to electrostatic electricity, for example when a "charged" person handles the array or touches its connector terminals. It has been ascertained that this is due to the high resistivity of the connection between the shield and the "common" connector terminals. The referenced patent application solves the problem by connecting the shield to the common circuit run near both ends of the flash array, reducing the resistance between the shield and the common connector terminals.